Impacts of Southern Ocean warming on marine connectivity
Photos copyright of Dr Mike Meredith, BAS
It is well established that at higher temperatures, larvae that rely on yolk resources for nutrition will exhaust these supplies more quickly at higher temperatures, meaning they may not reach appropriate feeding grounds in time to develop into adults.
In such circumstances, fewer young will recruit to the next generation of individuals, and since dispersal among sites will be reduced, populations would be expected to lose connectivity, which has follow-on effects on population and ecosystem resilience.
We will examine how likely such effects are by observing fish larvae of several species differing slightly in their life history larval characteristics, and compare their rates of development in relation to fluctuations in temperature. We test whether higher temperatures do indeed lead to faster development by two means: (1) with live larvae acclimated to different temperatures regimes within a season, and (2) with archived larval specimens sampled from the wild across multiple years in which developmental temperature regimes varied. We will use these data to inform species-specific Individual Based Models incorporating ocean circulation and biological characteristics for each species.
This allows us to test whether any changes in rate of development will influence the likelihood of larvae reaching appropriate feeding grounds and recruiting to the adult population. Model predictions of dispersal for the present-day will be validated by comparison with inferred dispersal from genetic analyses, and an assessment of dispersal variability due to interannual oceanographic variability will allow the effects of increased temperature to be placed in context.
For example, this movie shows predicted C. gunnari and N. rossii dispersal following spawning at the South Shetland Islands in 2000. By adjusting developmental rates, and thus the simulated planktonic periods, the effect of increased temperatures on the predicted connectivity can be assessed.
Simulated fish egg/larval transport for spawning of C. gunnari (left) and N. rossii (right) at the South Shetland Islands - Emma Young, British Antarctic Survey.
It will then be possible to make predictions about the likely effects of the predicted increases in temperature in the area on fish recruitment as a component of climate change. Such information is important since climate records from the Antarctic show that the waters of the Antarctic are warming more rapidly than the global ocean as a whole. Not only is this significant for much of the biodiversity that is unique to the Antarctic, but the Southern Ocean is known to influence climates globally. Ultimately, our integration of environmentally relevant data taken from nature, with genetically validated biophysical models will enable a more realistic projection of the impact of ocean warming on marine species and ecosystems.